The purpose of the research is to investigate the modification of territorial aggressive behavior through the control of the balance of brain catecholamines and indolamines simply and directly by regulating the availability of their precursor amino acids. One of the main objectives of the research is to test the hypothesis that a dietary imbalance resulting in a phenylalanine excess increases arousal and aggression, and that an imbalance favoring tryptophan opposes it. Treatment conditions consist of male CF-l mice maintained on semisynthetic diets supplemented with L-phenylalanine, L-tryptophan, or L-leucine at different levels in the range, 0.25 - 4.0%, of diet (replacing a small part of the dietary carbohydrate). Behavioral consequences of the different diets are determined using a highly reliable territorial aggression test, standardized with use of more than one thousand CF-1 male mice. Other measures such as open-field behavior and rotorod performance are also obtained in order to assess any effects on locomotor activation and coordination. The overall objectives of the total project are to determine the time course of the effects of the diets, and the relations among concentrations of amino acids in the diet, in the blood, in the brain, the endogenous levels and synthesis of brain norepinephrine, dopamine, and serotonin, and the relation of these to the display of territorial aggression in mice.